Much attention has been given in recent times to energy policy and energy conservation generally, and to electric power generation and transmission in particular. Traditional models for power generation and distribution may once have been the only workable ways to deliver power to end users. But a variety of factors including political events, rising energy costs, technological progress, and concern for the environment have drawn attention to the need for new paradigms and approaches.
It is apparent that one important goal is to make it possible to draw upon distributed energy resources as a source of electric power for end users. There are, however, a number of forces seemingly conspiring to limit or frustrate the use of distributed energy resources. One problem is that the operators of commercial power grids refuse to permit large amounts of power to be fed into the grid from end-user locations. Typically the operator of a commercial power grid will permit feeding of such power only up to a very small percentage of the distribution capacity of the grid. This means that if one end-user location happens to have a large amount of locally generated power available, it is likely to be difficult or impossible to use the commercial power grid as a way to distribute that power to other end user locations.
It would thus be very desirable if a workable approach could be found for passing large amounts of power from one end-user location to another, despite the lack of cooperation on the part of the operator of the commercial power grid.
As will be discussed in more detail below in connection with the invention, experience reveals that moving electric power from one part of an end-user location to another, or from one end-user location to another, in an efficient and reliable way, is not easy. Traditional ways of passing power from one grid to another have many drawbacks. In more recent times, inverters have been developed that convert DC to AC in an efficient fashion and with improved quality of alternating current. But the inverters, taken singly, do not serve the end users as well as might be desired.
It would be very helpful if an approach could be found for coordinating the frequency and phase of generated AC so as to avoid conflicts among the two or more inverters that might be connected to a given AC power bus.
Patents of possible background interest include U.S. Pat. No. 7,145,266 to Lynch, et alia entitled Parallel-connected inverters with separate controllers having impedance current regulators, U.S. Pat. No. 7,116,010 to Lasseter et alia, entitled Control of small distributed energy resources, and U.S. Pat. No. 6,693,409 to Lynch, et alia entitled Control system for a power converter and method of controlling operation of a power converter.